Linearizing drive for variable attenuators



F. GUDAITIS 2,865,007

LINEARTZING DRIVE FOR VARIABLE ATTENUATORS Dec. 16, 1958 Filed Aug. 9, 1954 INVENTOR. TRFNK DAITls JYl" TORNEY LINEARIZING DRIVE For: VARIABLE ATTENUATORS Frank Gudaitis, Brooklyn, N. Y., assignor to Polytechnic Research & Development Company, Inc., Brooklyn, N. Y., a corporation of N ew'York Application August 9, 1954, Serial b. 448,622 6 "Claims. (Cl. ass-s1 wave guide but is shifted laterally therein to vary the amount of attenuation. Q

A primary object of the invention is to provide a linearizing drive for a variable attenuator which is economical to manufacture. Another object of the invention is to providea linearizing drive for a variable attenuator wherein the range of attenuation and sensitivity of adjustment may be easily varied. 1

A further object is to devise for varying the insertion of an attenuator plate by movement of a control member along a path substantially parallel with the wave guide.

According to the invention, thecontrol member comprises a slide mounted upon a trackway arranged generally parallel with the section of 'wave guide containing the attenuator plate. The slide engages a cam surface on the support of the attenuator plate and movement of the slide along the trackway varies the amount of insertion of the attenuator plate into the w ave guide, or shifts the position of the plate within the wave guide. The cam surface on the attenuator plate support may be straight or curved, depending upon the relationship desired between the 'motionof the slide and the motion of the attenuator plate. 7

One embodiment of the invention, as applied to a fia ttype of attenuator, is shown in the accompanying drawingin which: j i 1 Figure l is a side elevational view of an attenuator having a linearizing drive in which the cam surface on the plate support is a straight surface;

Figure 2 is a top view of Figure 1;

Figure 3 is a side elevational view on a reduced scale of a modified plate support having a curved cam surface; and

Figure 4 is an end elevational view same reduced scale.

A wave guide section 1 having coupling flanges 2 on eachend is provided with a flap attenuator comprising a bar 4'- carrying an attenuator plate 5 in a position to move'in and out of a slot formed in the upper broad Wall of wave guide section 1. Bar 4 is hinged at one end on a horizontal axis by two horizontally mounted leaf springs 6 attached to the top of a fixed block 8 and to the lower surface of 'bar 4, and two vertically mounted springs 7 attached to the left end of bar 4 and the right side of block 8. The upper right edge of block 8 and the lower left edge of bar 4 are cut away to avoid interference with the action of springs 6 and 7. The springs are initially formed with a bend in them so they tend to of Figure 3 on the nited States Patent rotate bar 4 in a counterclockwise direction. The springs 6 and 7 provide a hinged joint free from sliding contact between relatively movable parts, and without any play between the parts.

Two vertical standards 10a are mounted on the wave guide section 1 on opposite sides of bar 4 near one end thereof and a second pair of vertical standards 10b are likewise mounted near the other end of bar 4. The

standards may be threaded and be held in position by nuts 11 threaded on the standards and engaging the top and bottom faces of the wave guide section. Standards Illa are joined by a cross-bar 12a and standards 1% are joined by a similar cross-bar 12b. The cross-bars are secured to the standards by nuts 13 to permit vertical adjustment of the cross-bars along the standards. The holes through which standards 10 extend are somewhat larger in diameter than the standards to allow a limited amount of angular movement of the cross-bars 12 with respect to the standards. The surface of these nuts which engage the cross-bars is hemispherical in shape and the height of each cross-bar above the wave guide 1 is adjusted by running the nuts 13 up or down the standards as required. The two cross-bars are joined by a pair of parallel track rails 14a and 14b which have mounted thereon a slide 15. A roller 16. is mounted on the lower side of slide 15 at the right end'thereof by means of a transverse pin 17 passing through two lugs extending downwardly from the body of the slide. Roller 16 acts as acarn follower and rolls along the upper surface of bar 4, which forms the cam surface or trackway for the wheel 16 as the slide 15 moves along rails 14a and 14b. A thumb screw 20 is threaded into the slide 15 and engages one of the track rails to clamp the slide in fixed position when desired. A graduated scale 21 is mounted between cross-bars 1211' and 12b parallel with the guide rails, and vernier scale 22 is mounted on the slide 15 adjacent the scale 22 for use in accurately setting the position of the slide.

g With the cross-bars adjusted as shown in the drawing (bar 12a at a higher elevation than bar 12b) and with the slide 15 at the extreme right end of its'travel, the attenuator plate 4is fully inserted into the wave guide 1. If the slide 15 is'moved to the extreme left end of its travel the attenuator plate will be withdrawn from the wave guide 1 by the action of springs 6 and 7 and will assume the position shown in dotted lines in Figure 1. Intermediate positions of the attenuator plate are obtained by setting the slide 15 at a suitable intermediate point along the trackway. Due to the angular relation between the center line of the wave guide 1 and the center lines of guide rails 14a and 14b, a given increment of movement ofslide 15 will result in a larger angular movement of attenuator plate when the slide is near the left end of its trav'el than when it is near the right end. The same effect could be obtained by setting the guide rails parallel with the wave guide 1 and tapering the bar 4 in its vertical dimension. However, the arrangement described and shown is capable of adjustment to give a variety of ranges of attenuation, whereas an arrangement utilizing parallel guide rails and a tapered bar would not be readily adjustable. If desired, the cam surface forming the track for roller 16 may take the form of a curved surface instead of a straight surface. One method of accomplishing this is shown in Figures 3 and 4 in which a cam strip 4a is mounted on the top of bar 4 in a position to engage roller 16, the upper edge of the strip being curved to provide the desired variation in attenuation with changes in position of the slide 16.

From the foregoing it will be seen that movement of the attenuator element transversely of the wave guide is effected by movement of the slide along the trackway which fixes the path of movement of that part of the slide (the cam follower 16) which engages the cam surface provided on the support for the attenuator element. The transverse movement of the attenuator element is effected by arranging the parts so that the path of movement of the slide roller is at an angle to and intersects the cam surface on the attenuator element support. By providing for angular adjustment of the trackway with respect to the wave guide, or for angular adjustment of the cam surface with respect to the attenuator element, different variations in attenuation may be obtained over the range of movement of the slide.

I claim:

1. A variable attenuator comprising a waveguide section having a longitudinal slot in one wall thereof, an attenuator plate inserted intosaid slot, means mounting said plate for movement into and out'of said waveguide by pivotal movement about a .point adjacent one end of said plate, two pair of standards mounted on said waveguide, one pair adjacent each end of said slot and straddling said slot, a cross-bar connecting each pair of standards, a pair of parallel track rails connecting said cross-bars, a slide mounted on said rails and having a roller mounted thereon, and a member secured to and movable with said plate and having a cam surface formed thereon within the path of movement of said roller, whereby upon movement of said slide along said rails said roller engages said cam surface and varies the penetration of said plate into said waveguide.

2. An attenuator in accordance with claim 1 and including means for adjusting the position of said crossbars on said standards whereby the position of said track rails may be adjusted with respect to said waveguide.

3. A variable attenuator comprising a waveguide section having an attenuator element mounted therein for movement transversely of the waveguide, a drive for said attenuator element comprising an elongated cam bar mounted outside of said section and extending along the length thereof, a track rail rigidly supported on said waveguide section and arranged generally parallel with said cam bar, a slide mounted for movement on said track rail and having a cam follower arranged to engage said cam bar throughout the extent of movement of said slide, means resiliently maintaining contact between said cam bar and said follower, the distance between said cam bar and the path of travel of said follower varying along the length of said bar whereby movement of said slide along said track rail effects movement of said attenuator element transversely of said waveguide section, and adjustable supporting means at one end of said track rail for adjusting the angular position of the path of travel of said follower with respect to the axis of said waveguide section.

4. A variable attenuator comprising a waveguide section, a flap attenuator mounted on said waveguide sec tion and having an attenuator plate arranged to penetrate saidwaveguide section in varying degrees by pivotal movement thereof about a mounting axis, a track rail rigidly supported on said waveguide section, said track rail extending longitudinally of said section, a slide mounted on said track rail for movement longitudinally of said section, an elongated cam element rigidly connected to said attenuator plate and extending along said section between said section and said track rail, a cam follower carried by said slide to engage said cam element, means resiliently maintaining contact between said cam and said follower, the distance between said cam and the path of travel of said follower varying longitudinally of said section whereby movement of said slide along said track rail varies the penetration of said attenuator plate into said section, and means at each end of said track rail for-adjusting the position of said track rail with respect to said waveguide.

5. A variable attenuator comprising a waveguide section having a longitudinal slot in one wall thereof, an attenuator plate inserted into said slot, means mounting said plate for movement into and out of said waveguide by pivotal movement with respect to said waveguide, a standard mounted adjacent one end of said slot, a standard mounted adjacent the other end of said slot, a track rail supported by said standards in spaced relation to said slot extending longitudinally of said slot, a slide mounted on said rail and having a roller mounted thereon, a cam bar secured to and movable with said plate and having a cam surface formed thereon to be engaged by said roller, means resiliently urging said cam bar against said roller with said roller being movable along said cam surface throughout sliding movement of said slide on said rail whereby upon movement of said slide along said rail said roller varies the penetration of said plate into said waveguide.

6. An attenuator in accordance with claim 5 including means for independently adjusting said rail on each of said standards to vary the angular direction of said rail with respect to the axis of said waveguide section.

References Cited in the file of this patent UNITED STATES PATENTS 2,563,868 Reichard Aug. 14, 1951 2,591,329 Zaleski Apr. 1, 1952 2,596,458 Zaleski May 13, 1952 2,646,551 Roberts July 21, 1953 2,669,027 Wilson Feb. 16, 1954 FOREIGN PATENTS 591,369 Great Britain Aug. 15, 1947 1,097,796 France Feb. 23, 1955 

